Overview
Postfix is one of the most widely used Mail Transfer Agents (MTAs) on Linux servers. Monitoring Postfix ensures your mail infrastructure delivers messages reliably, queues stay healthy, and bounce rates remain low.
Prerequisites
- A Linux server running Postfix
- Xitogent agent installed on the server
- An active Xitoring account
Step 1 — Install Xitogent
curl -s https://xitoring.com/install.sh | sudo bash -s -- --key=YOUR_API_KEY
Step 2 — Enable the Postfix Integration
Run the integration command and select Postfix:
sudo xitogent integrate
Select Postfix from the list. Xitogent will automatically detect your Postfix configuration and begin collecting metrics.
Key Metrics to Monitor
| Metric | Description |
|---|---|
| Queue Size | Number of messages waiting in the mail queue |
| Delivery Rate | Messages successfully delivered per minute |
| Bounce Rate | Percentage of messages that failed delivery |
| Deferred Messages | Messages temporarily queued for retry |
| Rejected Connections | SMTP connections rejected by Postfix |
| Active/Incoming Queue | Messages currently being processed |
Step 3 — Configure Triggers
- Queue Size (Warning) — Alert when the mail queue grows beyond a threshold, indicating delivery delays
- Bounce Rate (Critical) — Fires when bounce percentage spikes, which may signal blacklisting or DNS issues
- Deferred Messages (Warning) — Triggers when too many messages are stuck in retry state
Best Practices
- Monitor queue size trends — A steadily growing queue often indicates downstream delivery problems
- Track rejection reasons — High rejection rates may mean your server is under spam attack or misconfigured
- Set up SMTP uptime checks — Create Xitoring SMTP checks on port 25/587 to verify the service is accepting connections externally
- Combine with DNS monitoring — MX record issues directly impact mail delivery; monitor your DNS records with Xitoring
Troubleshooting
- No metrics appearing: Ensure Postfix is running with
systemctl status postfix - Queue growing rapidly: Check
/var/log/mail.logfor delivery errors and verify DNS resolution - High bounce rate: Verify your server IP is not on blacklists and SPF/DKIM records are correct